1. Field of the Invention
Exemplary embodiments of the present invention relate to a Light-Emitting Diode (LED) luminescence apparatus using Alternating Current (AC) power and, more particularly, to an LED luminescence apparatus that is capable of improving power factor and Total Harmonics Distortion (THD) and effectively dealing with the distortion and commercial AC voltage and variation in the magnitude thereof. Exemplary embodiments of the present invention also relate to an LED luminescence apparatus equipped with a driving circuit, which defines the characteristic range of total LED driving voltage (Vf) and uses LEDs having a plurality of driving voltages, thus decreasing a flicker phenomenon and increasing the quantity of light while minimizing an interval in which the LEDs are turned off.
2. Discussion of the Background
FIG. 1 is a block diagram of a conventional LED luminescence apparatus using AC power.
The conventional LED luminescence apparatus using AC power 1 is configured to provide unidirectional ripple voltage, output from a rectification circuit 2 that is implemented using a bridge circuit, to high voltage LEDs 3-1 to 3-4 via a resistor 4.
In such a conventional LED luminescence apparatus using AC power, LED driving current provided to the LEDs may not have a complete sinusoidal wave form and there may be a phase difference between the LED driving current and AC voltage, and therefore a problem may arise in that electrical characteristics, including power factor and THD, do not fulfill requirements for LED lighting.
In order to solve this problem, there is a method of reducing LED driving voltage (forward voltage: Vf). However, since the driving efficiency and light output characteristics of high-voltage driven LEDs may be determined depending on the driving voltage Vf of the LEDs, the simple reduction in the driving voltage Vf of the LEDs may cause the problem of not fulfilling the power factor and the THD that are presented in the LED lighting standard.
Furthermore, commercial AC power may not provide AC voltage in ideal sinusoidal wave form. That is, the problem of the magnitude of commercial AC voltage being higher or lower than that of a reference voltage in ideal sinusoidal wave form arises, and the waveform thereof may be distorted by harmonics.
FIG. 2A and FIG. 2B are waveform diagrams showing the waveforms of current, each of which is provided to LEDs and is subject to variation in AC power or the distortion of the AC power, in the conventional LED luminescence apparatus over time.
When the instantaneous voltage of an input voltage exceeds the driving voltage Vf of the LEDs, a driving current flows in proportion to the input voltage. As shown in FIG. 2A and FIG. 2B, the driving current of LEDs may be distorted by such deformation of the waveform of AC voltage. As a result, when LEDs are driven using AC power, the light emission efficiency of the LEDs may significantly vary depending on the shape and magnitude of the driving current.
Further, in order to drive LEDs using AC power, various circuits such as a rectification circuit, a power supply circuit, a voltage detection circuit, a pulse generation circuit, a switch circuit, and a current control circuit may be required.